private async Task Pulse(Button btn)
{
var original = btn.Scale;
foreach (var i in new[] { 1, 3 })
{
await btn.RelScaleTo(0.09 / i, 190, Easing.SpringOut);
await btn.RelScaleTo(-0.09 / i, 140, Easing.SpringOut);
btn.Scale = original;
}
}